Marine invertebrates

The 49th plate from Ernst Haeckel's Kunstformen der Natur, 1904, showing various sea anemones classified as Actiniae, in the Cnidaria phylum

Marine invertebrates are all multicellular animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates, lack a vertebral column. Some have evolved a shell or a hard exoskeleton.

As on land and in the air, invertebrates make up a great majority of all macroscopic life, as the vertebrates makes up a subphylum of one of over 30 known animal phyla, making the term almost meaningless for taxonomic purpose. Invertebrate sea life includes the following groups, some of which are phyla:

Acoela, among the most primitive bilateral animals;
Annelida, (polychaetes and sea leeches);
Brachiopoda, marine animals that have hard "valves" (shells) on the upper and lower surfaces ;
Bryozoa, also known as moss animals or sea mats;
Chaetognatha, commonly known as arrow worms, are a phylum of predatory marine worms that are a major component of plankton;
Cephalochordata represented in the modern oceans by the lancelets (also known as Amphioxus);
Cnidaria, such as jellyfish, sea anemones, and corals;
Crustacea, including lobsters, crabs, shrimp, crayfish, barnacles, hermit crabs, mantis shrimps, and copepods;
Ctenophora, also known as comb jellies, the largest animals that swim by means of cilia;
Echinodermata, including sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, crinoids, and sea daisies;
Echiura, also known as spoon worms;
Gnathostomulids, slender to thread-like worms, with a transparent body that inhabit sand and mud beneath shallow coastal waters;
Gastrotricha, often called hairy backs, found mostly interstitially in between sediment particles;
Hemichordata, includes acorn worms, solitary worm-shaped organisms;
Kamptozoa, goblet-shaped sessile aquatic animals, with relatively long stalks and a "crown" of solid tentacles, also called Entoprocta;
Kinorhyncha, segmented, limbless animals, widespread in mud or sand at all depths, also called mud dragons;
Loricifera, very small to microscopic marine sediment-dwelling animals only discovered in 1983;
Merostomata; also known as horseshoe crabs;
Mollusca, including shellfish, squid, octopus, whelks, Nautilus, cuttlefish, nudibranchs, scallops, sea snails, Aplacophora, Caudofoveata, Monoplacophora, Polyplacophora, and Scaphopoda;

Ernst Haeckel's 96th plate, showing various invertebrates classified as Chaetopoda in the Annelida phylum

Myzostomida, a taxonomic group of small marine worms which are parasitic on crinoids or "sea lilies";
Nemertinea, also known as "ribbon worms" or "proboscis worms";
Orthonectida, a small phylum of poorly known parasites of marine invertebrates that are among the simplest of multi-cellular organisms;
Phoronida, a phylum of marine animals that filter-feed with a lophophore (a "crown" of tentacles), and build upright tubes of chitin to support and protect their soft bodies;
Placozoa, small, flattened, multicellular animals around 1 millimetre across and the simplest in structure. They have no regular outline, although the lower surface is somewhat concave, and the upper surface is always flattened;
Porifera (sponges), multicellular organisms that have bodies full of pores and channels allowing water to circulate through them;
Priapulida, or penis worms, are a phylum of marine worms that live marine mud. They are named for their extensible spiny proboscis, which, in some species, may have a shape like that of a human penis;
Pycnogonida, also called sea spiders, are unrelated to spiders, or even to arachnids which they resemble;
Sipunculida, also called peanut worms, is a group containing 144–320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms;
Tunicata, also known as sea squirts or sea pork, are filter feeders attached to rocks or similarly suitable surfaces on the ocean floor;
Some flatworms of the classes Turbellaria and Monogenea;
Xenoturbella, a genus of bilaterian animals that contains only two marine worm-like species;
Xiphosura, includes a large number of extinct lineages and only four recent species in the family Limulidae, which include the horseshoe crabs.

Minerals from sea water

There are a number of marine invertebrates that use minerals that are present in the sea in such minute quantities that they were undetectable until the advent of spectroscopy. Vanadium is concentrated by some tunicates for use in their blood cells to a level ten million times that of the surrounding seawater.^[1] Other tunicates similarly concentrate niobium and tantalum.^[1] Lobsters use copper in their respiratory pigment hemocyanin, despite the proportion of this metal in seawater being minute.^[2] Although these elements are present in vast quantities in the ocean, their extraction by man is not economic.^[3]

References

1 2 Ruppert, Edward E.; Fox, Richard, S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th edition. Cengage Learning. p. 947. ISBN 81-315-0104-3.
↑ Ruppert, Edward E.; Fox, Richard, S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th edition. Cengage Learning. p. 638. ISBN 81-315-0104-3.
↑ Carson, Rachel (1997). The Sea Around Us. Oxford Paperbacks. pp. 190–191. ISBN 0195069978.

List of Animal Phyla

Aquatic ecosystems – general and freshwater components

General	Acoustic ecology Adaptation Agent-based models Algal bloom Anoxic waters Aquatic animals (Insects Mammals) Aquatic plants Aquatic science Benthos Biodiversity research Bioluminescence Biomass Biomonitoring Cascade effect Colored dissolved organic matter Camouflage and mimicry Dead zone Ecohydrology Ecosystems Eutrophication Fisheries science Food chain Food web GIS and aquatic science Hydrobiology Hypoxia Isotope analysis Microbial ecology Microbial food web Microbial loop Nekton Neuston Particle Pelagic zone Photic zone Phytoplankton Plankton Pleuston Predation Productivity Ramsar Convention Respiration Schooling Sediment trap Siltation Spawning Substrate Thermal pollution Toxicology Trophic level Water column Zooplankton More...

Freshwater	Biology Biomes Ecosystems freshwater lake river Fish Hyporheic zone Limnology Lake stratification Macrophyte Pond Fish pond Rheotaxis Stream bed Stream pool Trophic state index Upland and lowland Water garden Wetland brackish marsh freshwater marsh swamp bog fen Environmental quality More...

Ecoregions	Freshwater (List) Marine (List) The Everglades Maharashtra The North Pacific Subtropical Gyre The San Francisco Estuary

Aquatic ecosystems – marine components

Marine	Marine biology Marine chemistry Deep scattering layer Diel vertical migration Ecosystems large marine marine) f-ratio Iron fertilization Marine snow Ocean nourishment Oceanic physical-biological process Ocean turbidity Photophore Thorson's rule Upwelling Whale fall More...

Marine life forms	Bacteriophages Census Fish coastal coral reef deep sea demersal pelagic Deep sea communities Deep sea creature Deep-water coral Invertebrates Larvae Mammals Paradox of the plankton Reptiles Seabirds Seashore wildlife Vertebrates Wild fisheries

Marine habitats	Bay mud Black smokers Coastal biogeomorphology Cold seeps Coral reefs Davidson Seamount Estuaries Intertidal ecology Intertidal wetlands Kelp forests Hydrothermal vents Lagoons Mangroves Marine biomes Marine habitats Mudflats Rocky shores Salt marshes Salt pannes and pools Seagrass meadows Sponge reefs Tide pools

Issues	Ecological values of mangroves Fisheries and climate change HERMIONE Marine conservation Marine conservation activism Marine pollution Marine Protected Area

Marine ecosystems

Marine	f-ratio Iron fertilization Iron Hypothesis Large marine ecosystem Marine biology Marine ecosystem Marine snow Ocean chemistry Ocean fertilization Ocean turbidity Oceanic physical-biological process Photophore Thorson's rule Upwelling Whale fall more ...

Marine life forms	Census of Marine Life Coastal fish Coral reef fish Deep sea communities Deep sea creature Deep sea fish Deep-water coral Demersal fish Marine bacteriophage Marine invertebrates Marine larval ecology Marine mammal Marine reptile Marine vertebrate Paradox of the plankton Pelagic fish Seabird Seashore wildlife Wild fisheries

Marine habitats	Bay mud Black smokers Coastal biogeomorphology Cold seeps Coral reefs Davidson Seamount Estuaries Hydrothermal vents Intertidal ecology Intertidal wetlands Kelp forests Lagoons Mangroves Marine biomes Marine habitats Mudflats Rocky shores Salt marshes Seagrass meadows Sponge reefs Tide pools

Issues	Ecological values of mangrove Fisheries and climate change HERMIONE Marine conservation Marine conservation activism Marine pollution Marine protected area

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Marine invertebrates

Minerals from sea water

See also

References